Intermediate members for the crossing points of tennis racket stringings

ABSTRACT

Intermediate members for the crossing points of tennis racket stringings in which the intermediate members are formed as crosspiece guides having crossing tubular or, respectively, groove-shaped portions, which at least partly encompass the strings by means of suitable wings, and which are constituted of a relatively low-friction, self-lubricating plastic or synthetic material.

United States Patent Dischinger 1 Nov. 25, 1975 [541 INTERMEDIATE MEMBERS FOR THE 3,375,815 4/1968 Novak 124/30 A X C O G POINTS O TENNIS RACKET 3,381,959 5/1968 LeFiel|..., 273/68 STRNGINGS 3,612,545 10/1971 Storms.... 273/DIG. 4 3,769,956 11/1973 Simo 273/73 D UX [751 Inventor: 22 1: Bremen FOREIGN PATENTS OR APPLICATIONS y 24,856 11/1913 United Kingdom 273/73 D [73] Assignee: Babolat-Maillot-Witt, Lyon, France 1,398,833 4/1965 France 273/73 D 640,448 3/1928 France.... 273/73 D [22] Wed: 301 1973 786,619 6/1935 France 273/73 D [30] Foreign Application Priority Data Dec. 1, 1972 Germany 2258872 [52] US. Cl 273/73 R; 273/73 D; 273/DIG. 4 [51] Int. Cl. A63B 51/00 [58] Field of Search 273/73 R, 73 D, DIG. 4, 273/D1G. 12, DIG. 29, 68; 124/30 A, 41 A [56] References Cited UNITED STATES PATENTS 1,682,199 8/1928 Smilie 273/73 D 2,542,661 2/1951 Godfrey.... 273/73 D 3,065,567 11/1962 Lemelson 273/DIG. 4 3,190,032 6/1965 Green et a1. 273/DlG. 4 3,232,286 2/1966 Guyton 124/41 A X 3,252,241 5/1966 Gould 273/DIG. 4

OTHER PUBLICATIONS Dupont Information Bulletin: Teflon 100 FEP; June 1960, pp. 1-3. Archery Magazine, Vol. 34, Aug. 1962, p. 35.

Primary Examiner-Richard J. Apley Attorney, Agent, or Firml-laseltine, Lake & Waters [57] ABSTRACT Intermediate members for the crossing points of tennis racket stringings in which the intermediate members are formed as crosspiece guides having crossing tubular or, respectively, groove-shaped portions, which at least partly encompass the strings by means of suitable wings, and which are constituted of a relatively lowfriction, self-lubricating plastic or synthetic material.

14 Claims, 13 Drawing Figures Low Fricllon Self-Lubrlcu'lnq Material e4. Poly/formaldehyde, Polytelrulluoroelhylene Polypropylene Polyamlde Bun Wllh A Molybdenum 0r Gmphlte Additive, And The Llke US. Patent Nov. 25, 1975 Sheet10f5 3,921,979

FIG.1

PRIOR ART FIG 2 Patent Nov. 25, 1975 Sheet2of5 3,921,979

Low Friction,

Self Lubricating Moleriol, e.g.Polyformoldehyde, Polyleirofluoroelhylene, Polypropylene,

Polyomide Bose With A Molybdenum Or Gruphile 23 Additive, And The Like FIGA US. Patent Nov. 25, 1975 Sheet 3 of 5 Low Frictlon SelfLubricuflng Material e.g. Polyformoldehyde, Polytelrufluoroerhylene Polypropylene,

Polyamide Bose With A Molybdenum Or Graphite Addlrive, And The Like US. Patent Nov. 25, 1975 Sheet40f5 3,921,979

FIGB

Low Friction j Self-Lubricahng Material e.g. Polyformuldehyde, Polytetrafluoroethflene Polypropylene,

Polycmide Base with A Molybdenum 0r Graphite Additive, And The Lkke FIG. 7(1

FIG.8 1

U.S. Pateznt Nov. 25, 1975 SheetSofS 3,921,979

INTERMEDIATE MEMBERS FOR THE CROSSING POINTS OF TENNIS RACKET STRINGINGS FIELD OF THE INVENTION The present invention relates to intermediate members for the string cross points of tennis racket stringings, and with the intermediate members including recess on both sides thereof adapted to receive the mutually crossed strings.

DISCUSSION OF THE PRIOR ART Presently known tennis racket stringings with gutstrings, which evidence, in comparison with synthetic material strings, a superior enhanced degree of elasticity and, consequently, an improved playing relationship, are however subject to the important disadvantage in that the life expectancy thereof, particularly in view of mechanical wear at the cross-over points between two strings, in contrast with synthetic strings, is relatively short. In order to avoid this disadvantage various known intermediate members are used, for example, in the shape of discs or plates formed of leather or the like, having recesses on both sides thereof adapted to receive the mutually crossing strings. These intermediate members are relatively stiff and are intended to form, by means of an increase in the coefficient of friction at the cross-over points, and intimate connection while preventing mutual displacement of the strings. However, in that case there is obtained, at the expense of the positive properties of gutstrings, a racket stringing having overall relatively poor elasticity characteristics and deficient playing properties, and which due to an unfavorable load distribution and unavoidable friction is readily damaged under impact loads.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide intermediate members for the string crossing points of tennis racket stringings which, without adversely affecting the degree of elasticity and resilience of the tennis racket stringings, will in an effective manner prevent the rapid destruction of the tennis racket strings.

The implementation of the object of the present invention is achieved in that the intermediate members are formed as crosspiece guides having crossing tubular or, respectively, grooveshaped portions, which at least partly encompass the strings by means of suitable wings, and which are constituted of a relatively lowfriction, self-lubricating plastic or synthetic material.

The inventive tennis racket stringing utilizes the collective advantages of the gutstrings, namely in particular, their outstanding elastic characteristics to the fullest extent, while concurrently preventing damage by a considerable reduction in the friction at the crossing points through the satisfactory guidance of the individual strings. From the foregoing there isachieved an outstanding elastic playing characteristic with a good traction capacity of the upper surface of the tennis racket stringing and thereby a better, and for the same load requirement. accelerated ball conveyance.

Although the inventive intermediate members or crosspiece guides are, above all, particularly suited for tennis racket stringings employing gutstrings, they may also be advantageously employed in connection with plastic or synthetic material strings so as to improve either the elasticity and/or the contact properties of the stringing,.as well as playing characteristics of the tennis racket.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is now described in detail with respect to various embodiments of the tennis racket stringing, having reference to the accompanying drawings, in which:

FIG. 1 illustrates a perspective, partly sectioned and enlarged fragmentary view of a typical tennis racket stringing showing the impact load thereon during impact by a tennis ball;

FIG. 2 is a schematic representation of sequential wear or chafing-through conditions of two crossed-over strings;

FIG. 3 shows a perspective representation of a crossing point provided with a crosspiece guide formed in accordance with a first embodiment of the invention;

FIG. 3a is a sectional view similar to FIG. 3 showing a crosspiece guide constructed according to a second embodiment;

FIG. 4 is a sectional view similar to FIG. 3 showing a crosspiece guide constructed according to a third embodiment;

FIG. 5 is a plan view of a portion of a tennis racket stringing having mounted thereon crosspiece guides constructed according to the embodiment of FIG. 3;

FIG. 6 is a sectional view taken along line VIVI in FIG. 5;

FIG. 7 is a side elevational view of a fourth embodiment of a crosspiece guide constructed according to the invention;

FIG. 7a is a bottom plan view of the crosspiece guide of FIG. 7;

FIG. 8 is a side elevational view similar to FIG. 7 of a slightly modified fifth embodiment of a crosspiece guide according to the invention;

FIG. 8a is a bottom plan view of the crosspiece guide of FIG. 8;

FIG. 9 is a plan view of a portion of a tennis racket stringing having mounted thereon crosspiece guides constructed according to the embodiment of FIGS. 7 and 7a; and

FIG. 10 is a sectional view taken along line X-X in FIG. 9.

DETAILED DESCRIPTION Referring now in greater particularity to the drawings, FIG. 1 illustrates in a fragmentary enlarged view, partly in section, a standard type of tennis racket stringing showing the deformation of the strings in the direction of arrow 10 upon impact by an oncoming tennis ball. Represented are a plurality of parallel, radially sectioned strings 14, and a string 16 extending perpendicularly thereto, and which is twisted through the strings 14 strings 16, as shown in FIG. I. The impact of the tennis ball 12 deforms the strings at the impact point approximately into the configuration schematically illustrated by string 16, in which the impulse of the tennis ball in the direction of the arrow 18 is transmitted to the strings, as is illustrated by the intermediate string 20. By means of this impulse, each string which is positioned above at the crossing point is compressed against the there-below positioned string (in the illustrated example against the string 16). Consequently, the approximately point-shaped contact surface between two crossing-over strings is widened into a larger contact surface having, for example, a width x.

Through the string which is located beneath each crossing point, for example, string 16, there is generated a reaction force extending in the direction of arrow 22. There is formed, concurrently an increase in the friction surface and an increase in the contact pressure, resulting in an extremely large frictional resistance between the two strings. Due to the elasticity of the individual strings, upon the back-and-forth movement of the stringing surface, and in particular during rebounding, which occasionally does not occur in a direction perpendicular relative to the stringing surface, an at least partially mutual string displacement becomes unavoidable. The thereby generated through-chafing or wear conditions are illustrated in FIG. 2 in four different stages thereof. Individual strings 14a, 14b, 14c and 14d which extend perpendicular to a transversely positioned string 16, and which are positioned therebelow at the crossing points 26a, 26b, 26c and 26d, evidence a widely divergent advancing wear appearances. Extending from the string 14a which characterizes the new condition of the tennis racket stringing, there are illustrated the sequentially increasing wear conditions of the contact surfaces 26b, 26c and 26d. The frictional wear finally leads to the condition in which one of the strings, upon impact by the tennis ball, fails to resist the load and consequently tears.

The various embodiments of FIGS. 3, 3a and 4 illustrate crosspiece guides 28, which are introduced between two crossing-over strings 16 and 20.

Referring to FIG. 3, showing a first embodiment of the invention, illustrated at least partly in section, this crosspiece guide comprises two perpendicularly extending tubularly or trough-shaped members 30, 32 which, by means of two symmetrical mirror-image shaped wings or side walls 34 and 36, encompass the strings l6 and 20 for about one-half their circumferences, and which then extend substantially parallel to each and tangential relative to the respective strings beyond the latter. This construction forms essentially groove-like depressions, in which the strings 16, 20 extend in side wall-contact with the contact wings 34, 36. This first embodiment is of particularly simple construction, and facilitates the rapid and uncomplicated insertion of the individual strings into the crosspiece guides. I

The second embodiment illustrated in FIG. 3a of the drawin'g' ge'nerally corresponds with that of FIG. 3, howv er., in this modification the tubular-like portions 430,32 only extend so as to encompass the strings 16, 20

for only approximately one-half the circumferences thereof. Inasmuch as the strings 16, 20 are under axial tension, a crosspiece guide 28 of the type described is in itself adequate to obtain an adequate guide and securing of the various strings 16, 20 in the region of the cross over points. In this embodiment it is also possible to effect the insertion of the strings 16, 20 into the respective curved recesses without the need for additional measures. Depending upon the occasion, the wings of the tubular-like members 30, 32 may be, according to any particular requirement, either shortened or lengthened.

In FIG. 4 there is illustrated a third embodiment of a crosspiece guide 28 in which the tubular-like members 30, 32 almost entirely encompass the strings 16, 20. The respective wing portions, as in the other embodiments, are symmetrically mirror-image shaped relative to each other, and their free ends bend into proximity to each other at the upper surface of each of the strings 16, 20. .In order to facilitate the subsequent application or replacement of the crosspiece guides 28 according to the embodiment, the wing portions of the tubularlike members 30, 32 are preferably elastically constructed so that the strings 16, 20, after bending open of the wings, are clampingly encompassed by the latter upon snapping shut of the wings.

While the embodiments of FIGS. 3 and 4 are in particular also adapted to prevent any direct impact contact by the oncoming tennis balls, which provides for a considerable reduction in mechanical wear, the embodiment of FIG. 3a is particularly simple in construction and in material savings. However, in common in all embodiments, due to the lack of friction in the region of the cross-over points, the various strings 16, 20 may be displaced relative to each other in an unhindered manner in response to any load or rotation imparted thereto.

In FIG. 5 there is illustrated a portion of a tennis racket stringing in which there are positioned crosspiece guides 28 constructed according to FIG. 3 a tithe cross-over points of the crossing strings 14, 16. From FIG. 6, which shows a sectional view of the stringing of FIG. 5 taken along line VI-VI, there may be clearly ascertained the inter-weaving of the individual strings l4 and 16. The tubular-like members 30, 32, whose wings 34, 36 extend up to or beyond the outer sides of the strings 16, 20, thereby prevent the direct contact between the ball and the strings in at least in the region of the cross-over points.

From FIGS. 7 and 7a there is ascertained in, respectively, side and plan views, a fourth embodiment of crosspiece guide 37. This crosspiece'guide structure includes relatively perpendicularly extending tubular-like members 38 and 40, which closely adhere to the string at the cross-over point and which are mutually reinforced through flanges 42. The tubular-like members 38 and 40 are, in the longitudinal direction of the recesses or bores 44 which are adapted to receive the strings, provided with a slot 46, by means of which they may elastically be bent apart so as to facilitate insertion of the string into the recess 44. Subsequently, the tubularlike member snaps closed and thereby fixedly retains the string in that position.

A fifth embodiment which largely corresponds with the fourth embodiment illustrated in FIGS. 7, 7a, i's ascertained from FIGS. 8 and 8a. The crosspiece guide crossing elements 37a shown therein comprises, in lieu of the tubular-like members, two mutually perpendicularly extending ridge-like members 38a, 40a which, in a manner similar to that of the embodiment of FIG. 3, serve as guide grooves for the strings (not shown). The outwardly projecting wings of the rigde-like members 38a and 40a may be formed as high as required, and

also different with respect to each other. Additionally, flanges 420 which interconnect the ridge-like members 38a, 40a serve as reinforcements therefore. The crosspiece guides 37a of this embodiment are somewhat simpler in construction than the crosspiece guides 37 of the fourth embodiment, since the ridge-like members 38a, 40a do not include ring-like closed and consequently elastically formed regions.

A section of a tennis racket stringing having crosspiece guides 37a of the type shown in FIGS. 7, 7a may be ascertained from FIG. 9 of the drawings. Therein it is clearly noticeable, that the tubular-like closed, and with suitable longitudinal slots provided portions 38, 40, encompass perpendicular to each other extending strings 14, 16, so as to guide and protect these in the regions of their cross-over points. These slots 46 extend in longitudinal directions in conformance with the re spective strings 14, 16.

In FIG. there is shown a sectional view taken along line X-X in FIG. 9, and from which there may be ascertained the sinuous interweaving of the individual strings 14, 16. Further, therein is illustrated the manner in which the tubular-like members 38, 40 adhere against the strings.

Furthermore, it is advantageous that the wings 34, 36 and/or the ridge-like members 380, 40a be profiled at the ends thereof for enhancing their gripping ability. Thereby, as indicated it becomes still simpler to impart a spin to the tennis ball during play and to improvedly guide the latter.

In order to have no frictional forces generated between the gutstrings l4, 16, and the individual crosspiece guides 28, 37 and 37a, and thereby at all crossover points for any two strings, it is preferable that the low-friction, self-lubricating synthetic or plastic material for the crosspiece guides be constituted of polyformaldehyde or polytetrafluoroethylene (Teflon). In lieu thereof it is also possible that the plastic material be constituted of a polypropylene or polyamide base with a molybdenum or graphite additive. These materials provide a practically negligible degree of friction even at higher forces caused by the axial tensioning of the strings.

Due to the almost frictionless mutual sliding of the strings within the crosspiece guides, the elasticity of the novel gutstring stringing is considerably increased above the elasticity for prior art tennis racket stringings. Independently of the advantage that the play with this type of tennis racket is considerably more comfortable and feel-sensitive, the player receives a considerably improved playing advantage due to the higher level of employment of the maximum elasticity characteristics of the gutstrings since, for example, by applying the same degree of force, the play is considerably accelerated. The crosspiece guides in the regions of the crossover points provide a good support for the individual strings and a satisfactory guide while concurrently preventing friction which would tend to cause damage, and allow for the sliding-through movement of the individual strings so as to render possible the unhindered use of their elastic characteristics.

In particular, the crosspiece guides employed in the stringing allow for the use of thinner gutstrings, which additionally enhances the elasticity, and reduces the cost of the tennis racket stringing.

While there has been shown what is considered to be the preferred embodiment of the invention, it will be obvious that modifications may be made which come within the scope of the disclosure of the specification.

What is claimed is:

1. An intermediate crosspiece guide member formed of a low-friction self-lubricating synthetic material for use in a tennis racket stringing having crossing gutstrings, said member adapted to be mounted intermediate the gutstrings at the crossings thereof, said member comprising first and second recessed portions on opposite sides thereof, said recessed portions each including groove-forming pairs of upstanding wings adapted to extend along and engage at least part of the outer surface of gutstrings adapted to be received in said recessed portions, the groove-forming wings of said first recessed portion extending in a parallel spaced plane and transversely of the groove-forming wings of said second recessed portion adapted to prevent contact between adjacent gutstrings at the crossing thereof and to concurrently guide said gutstrings in coplanar and transverse directions.

2. An improvement as claimed in claim 1, said synthetic material being polyformaldehyde.

3. An improvement as claimed in claim 1, said synthetic material being polytetrafluoroethylene.

4. An improvement as claimed in claim 1, said synthetic material being constituted of a polypropylene base and a molybdenum additive.

5. An improvement as claimed in claim 1, said synthetic material being constituted of a polypropylene base and a graphite additive.

6. An improvement as claimed in claim 1, said synthetic material being constituted of a polyamide base and a molybdenum additive.

7. An improvement as claimed in claim 1, said synthetic material being constituted of a polyamide base and a graphite additive.

8. An improvement as claimed in claim 1, each wing of said pair of upstanding wings being arcuately bent towards the other wing of said pair so as to form a substantially tubular configuration having a slot between the adjacent free ends of said wings.

9. An improvement as claimed in claim 8, said wings being elastically deformable.

10. An improvement as claimed in claim 1, each said pair of wings comprising symmetrical mirror-image shaped wings.

11. An improvement as claimed in claim 1, comprising reinforcing flange means connected to said grooveforming wings.

12. An improvement as claimed in claim 1, said wings each having profiled end portions.

13. An improvement as claimed in claim 1, said upstanding wings being curved so as to form a generally hemisphericallyshaped groove therebetween.

14. An improvement as claimed in claim 1, said upstanding wings of each pair having generally parallel wall portions. 

1. An intermediate crosspiece guide member formed of a lowfriction self-lubricating synthetic material for use in a tennis racket stringing having crossing gutstrings, said member adapted to be mounted intermediate the gutstrings at the crossings thereof, said member comprising first and second recessed portions on opposite sides thereof, said recessed portions each including groove-forming pairs of upstanding wings adapted to extend along and engage at least part of the outer surface of gutstrings adapted to be received in said recessed portions, the groove-forming wings of said first recessed portion extending in a parallel spaced plane and transversely of the groove-forming wings of said second recessed portion adapted to prevent contact between adjacent gutstrings at the crossing thereof and to concurrently guide said gutstrings in coplanar and transverse directions.
 2. An improvement as claimed in claim 1, said synthetic material being polyformaldehyde.
 3. An improvement as claimed in claim 1, said synthetic material being polytetrafluoroethylene.
 4. An improvement as claimed in claim 1, said synthetic material being constituted of a polypropylene base and a molybdenum additive.
 5. An improvement as claimed in claim 1, said synthetic material being constituted of a polypropylene base and a graphite additive.
 6. An improvement as claimed in claim 1, said synthetic material being constituted of a polyamide base and a molybdenum additive.
 7. An improvement as claimed in claim 1, said synthetic material being constituted of a polyamide base and a graphite additive.
 8. An improvement as claimed in claim 1, each wing of said pair of upstanding wings being arcuately bent towards the other wing of said pair so as to form a substantially tubular configuration having a slot between the adjacent free ends of said wings.
 9. An improvement as claimed in claim 8, said wings being elastically deformable.
 10. An improvement as claimed in claim 1, each said pair of wings comprising symmetrical mirror-image shaped wings.
 11. An improvement as claimed in claim 1, comprising reinforcing flange means connected to said groove-forming wings.
 12. An improvement as claimed in claim 1, said wings each having profiled end portions.
 13. An improvement as claimed in claim 1, said upstanding wings being curved so as to form a generally hemisphericallyshaped groove therebetween.
 14. An improvement as claimed in claim 1, said upstanding wings of each pair having generally parallel wall portions. 